Mating disks and rods into an ordered phase

Disk-shaped molecules tend to stack in columns, whereas rod-shaped ones tend to align parallel to each other. When the two types of molecules are mixed, they tend to phase separate. Yano et al. found the right recipe that allowed enough affinity between the disks and rods so that they formed a blended twisted columnar phase. The phase could be stabilized by polymerizing the disks. The orientation of the twisted columns could be altered using electric fields, whereas optical stimuli could lead to a second ordering transition.

Abstract

Disk- and rod-shaped molecules are incompatible in coassembly, as the former tend to stack one-dimensionally whereas the latter tend to align in parallel. Because this type of incompatibility can be more pronounced in condensed phases, different-shaped molecules generally exclude one another. We report that supramolecular polymerization of a disk-shaped chiral monomer in nematic liquid crystals comprising rod-shaped molecules results in order-increasing mesophase transition into a single mesophase with a core-shell columnar geometry. This liquid crystalline material responds quickly to an applied electric field, resulting in unidirectional columnar ordering. Moreover, it can be modularly customized to be optoelectrically responsive simply by using a photoisomerizable rod-shaped module. The modular strategy allows for cooperative integration of different functions into elaborate dynamic architectures.